A practical guide to TPMS

Nov. 2, 2017
Even though TPMS systems have improved and become easier to service it still takes practical experience and knowledge to keep work problem-free and profitable.

Tire pressure monitoring systems (TPMS) have definitely become easier to work with since they were first introduced a few years back and that’s a good thing. Not only is it difficult to work around or “fool” a TPMS system (for whatever reason) but leaving the MIL illuminated isn’t just annoying — it may actually cause problems for customers since TPMS is a safety-related vehicle system that shouldn’t be disabled.

But even though TPMS systems have improved and become easier to service it still takes practical experience and knowledge to keep work problem-free and profitable.

Usually not what you want to see after service. In this case the light came on after 15 minutes of driving and went off when the vehicle was shut off – only to return once again when the vehicle was driven for another 15 minutes (a new sensor and relearn fixed the problem).

In particular, it’s important to know about the things that can make a big difference when servicing the systems such as how to program replacement sensors quickly and effectively and also knowing if the system will need anything done after a routine wheel rotation or general service – and if special tools to service the system are required. Guessing incorrectly can definitely cause expensive problems.

Additionally, understanding how to prevent common issues from ever occurring in the first place (such as using extra caution around known leak points and knowing the things that tend to seize together before they break off and need to be replaced) and also how to successfully deal with the things that do go wrong (like sensors that don’t work or warning lights that come on at strange times) can prevent simple service issues from ever becoming big, time-consuming, money-losing headaches.

And it’s not difficult at all.

With a bit of knowledge and experience – and of course, having the right tools and components at hand – servicing TPMS systems doesn’t need to be problematic.

General service

Until recently one of the most common concerns (or fears) about working on a vehicle with TPMS was that performing general tire services like rotating wheels or installing or removing seasonal tires would affect the TPMS system and illuminate the warning light. Fortunately this isn’t as much of an issue anymore.

This truck came in with its TPMS light on and a quick visual inspection found that in addition to the TPMS issue it was also time for new tires – well past time, actually.

No doubt it’s still important to know if the system needs to be reset after service (or if newly installed wheel sensors need to be programmed and if so, how) so that the warning light won’t illuminate a few minutes after the customer picks up the vehicle.

But in general now, (always check service information and be sure) if there’s just one warning light or message for the whole system, it’s fairly safe to assume that the individual sensors likely won’t need to be manually programmed to new positions if a wheel is moved to another position on the vehicle – so there’s not likely to be issues rotating tires (but always check service information to be sure because there are exceptions). And it’s generally safe to assume that if there’s a separate reading displayed for each wheel, the system may indeed need to be reset if the wheel moves from its original position (in other words, relearned after tire rotation). But, again, check service information and be sure.

Also fortunately, TPMS relearning and programming is relatively simple to manage with the programming tool. Even better, since many newer vehicles have modules that can determine wheel position without being manually reprogramed this is becoming less and less of an issue. But, again, always check and be sure – never just blindly trust that the system will adapt on its own. It may not, and the system may illuminate the MIL or not function correctly.

However, if the vehicle does indeed need to be relearned it’s important to note that the procedure for relearning a sensor’s position on the vehicle varies among vehicles and manufacturers, and though it’s typically done using the tool (as directed by service information and usually prompted by the tool) just as there’s no single way of resetting oil change reminder lights or of programming ignition keys there’s also no single way of resetting TPMS systems. Save time and headaches by checking service information and finding out ahead of time what needs to be done.

Doing a bit of research can definitely prevent time-consuming problems from developing.

Tires can normally lose about 1 psi of pressure per month. However, wheels with missing valve caps can lose considerably more.

Another common TPMS fear was causing problems when switching from winter to summer wheels (or vice versa) – and even this isn’t as much of a problem anymore.

Many customers now use “cloned” TPMS sensors which eliminate the need to program new sensors when the wheels are changed. Customers usually mention when their seasonal wheels have “cloned” sensors and thanks to Internet chat rooms and online parts distributers this practice is surprisingly widespread and can work well. If this is the case, as with any other TPMS sensor, ensure there are no leaks when the wheels are installed and then ensure the warning light isn’t illuminated after service. Hopefully there are no issues.

However, if the sensors on the seasonal wheels do need to be programmed one tip (from experience) to keep in mind is that it’s important to have patience and to perform the procedure exactly as indicated in service information – and also to understand that it may not work successfully the first time.

Unfortunately even though TPMS systems have improved some vehicles still need more than one programming attempt before the process is successful – which is unfortunately something that hasn’t changed.

If the same rim is being used and just the tires are being changed then (from experience) it’s important to ensure the sensor doesn’t break or get damaged during service and also to ensure that no new leaks are created during the installation process.

To do this, it’s important to replace seals or other parts as directed in service information (or required because they’re obviously not fit for re-use) and also to be careful not to over-torque and damage the somewhat delicate TMPS components. This is important.

It’s not just important because over-torqueing breaks and warps things, which causes immediately noticeable problems, it’s also an important step because it prevents future problems from ever developing.

Leaks and breaks are fairly common so it’s wise to keep this in mind when working in the area. It’s better to prevent problems from occurring than to have to fix them later.

Repairs

Servicing the tire pressure sensors themselves (either because the tires are being changed or the sensor needs replacing) is usually straightforward and relatively simple but there are a few practical tips to keep in mind to keep the work problem-free.

This is rare but it did happen and it’s worth noting. This customer bought rims with the wrong size valve stem holes and the TPMS sensor wouldn’t fit. So the customer drilled another hole and installed a dummy valve 180 degrees from the working sensor. It’s still working.

Typically when replacing a TPMS sensor the tire is deflated and the retainer is unscrewed and the sensor then drops gently into the wheel. Then the tire is removed, the sensor is re-installed (with new seals or components) or replaced as required, and then the tire is re-installed and inflated, installed on the vehicle and then programed and relearned as required.

However, there are ways to keep this routine task both quick and problem-free.

One important thing to keep in mind is that not breaking the sensor off during service can actually be a bit tricky. Some manufacturers use metal valve caps on the sensors and unfortunately these can seize to the stems which can then break off when they’re removed (often with pliers) for routine service – not good at all.

Also, it’s important to know if the gasket and seals on the sensor will indeed need to be replaced, and if so to have them ready to use. The reason for this is obvious, seals often can’t be re-used and it’s good to have the replacements on hand so that new leaks aren’t created in the wheel. Again, the valve area is a notoriously common leak spot and it’s important to prevent this problem if at all possible,

This tire label got caught between bead and rim of this Lexus tire and caused a very tiny leak (less than half a psi every 300 miles). This would have likely gone unnoticed but the tire pressures were displayed at each wheel and the customer was fanatic about keeping the pressures equal. Resealing the wheel (after removing the sticker) fixed the problem

Finally, it’s important to make sure any manufacturer stickers are removed from the tire before it’s installed so the bead can seal to the rim thoroughly – not doing so can and does cause problems.

One Lexus customer brought their vehicle in because the pressure at a particular wheel would drop by 1 psi each week (all four wheel pressures were displayed so the difference was very noticeable). Turns out when new tires were installed the bar code sticker was never removed from the bead of the tire and there was indeed a small leak between the sticker and the rim. The wheel had to be broken down, resealed, and reinstalled to fix the problem.

Troubleshooting tips

Usually when the TPMS warning light illuminates the fault is repaired by sealing a leak, correcting tire pressures, patiently performing a relearn procedure, or by replacing a faulty sensor (or a combination of all these things).

However, as with any routine diagnosis, it helps to keep a few things in mind to prevent problems from developing.

As with any other troubleshooting, it’s important to start TMPS diagnosis by verifying that there actually is a problem and that the bulb comes on during bulb check and then goes off.

If there is actually is a problem, check all tire pressures, and adjust them if necessary, keeping in mind that it may take a few moments for the data to refresh and display accurately. Adding or removing air a little bit of air at a time tends to be the quickest way to get good results.

One important tip to keep in mind that using clean, dry air is very important – air lines that spray water everywhere can get water inside the TPMS sensor and cause problems to develop. One excellent tech I worked with insists that water from air lines damages more TPMS sensors than those spray cans of tire sealer and inflator ever will.

Continuing on, if a low tire is indeed present, be sure to also inspect the condition and wear patterns of all the tires in case they need to be replaced – and also because it’s better to notice exposed belts and sharp, damaged rims at this stage rather than when they go through your hand during service. It’s definitely better to find out early on if extra work is needed or if extra caution will be required during the repair.

If everything checks out okay but the system still indicated a tire with low pressure make sure the control module is seeing the sensors and receiving the data OK. It’s not uncommon for one sensor (or more) to be faulty and not send information to the control module. The sensors themselves have batteries that usually last for just over five years and the batteries aren’t replaceable – the whole sensor is replaced and subsequently programmed when the battery fails.

Metal valve caps – like this one – have been known to seize to the valve stem and undoing them with pliers can actually break the sensor. Best to prepare the customer beforehand if there’s any chance of damage during service and be sure to torque caps correctly.

Also, since the warning light is often controlled by the body control module, check that all of the fuses are good (most vehicles have several fuse centers that need to be checked) and note any other problems in the system such as aftermarket accessories or systems that interfere with electrical signals. Some sensors are sensitive to interference from other sensors and systems. In fact, some Toyota vehicles have QR stickers on the rim so that the techs can simply scan the code with the tool and program the sensor that way which is quicker and also prevents interference from being an issue (the stickers are supposed to be removed at PDI but have been known to be left in place). Checking for service bulletins or tech tips on this issue can definitely save diagnostic time.

If it is indeed evident that a sensor isn’t being read correctly, one tip that may help is to try leaning the same type of tire-sensor-rim combination against the suspect wheel and seeing if the control module can read it (easier to do if you service many of the same vehicles). If the “donor” sensor registers, suspect a bad sensor and proceed from there – usually this means replacing the sensor, programming it, then performing a relearn if required but, as always, check service information and be sure.

And if the sensors are being indeed read and the system still indicates that a wheel has low pressure and you’ve tried everything and are out of ideas, from experience, try reprogramming each sensor and then resetting the system. Sometimes this needs to be done more than once but it’s been known to fix the problem. Again, always consult service information – service bulletins and tech tips in particular – but from experience, carefully following the steps exactly as directed using the correct tool (and repeating, patiently, if needed) fixes many TPMS problems. Just be sure to road test the vehicle and verify the repair before releasing the vehicle – TPMS MIL indicators often come on after a few minutes of driving, not right away at start up.

There’s no single way of programming tire pressure monitor sensors that applies to all vehicles – and there are some interesting methods out there. For example, the sticker on this Toyota’s rim is for the tire pressure monitor code. The QR code is scanned with the reprogramming tool, making programming quicker and avoiding any interference from surrounding electronics.

Conclusion
Depending on where in the country you work and what type of vehicles you service TPMS systems may never cause you a day of stress, or may cause so many problems that the sensors are assembled ahead of time and kept ready to install as needed. From experience, vehicles that go off road or have many aggressive drivers (like fleets of work trucks) are very hard on the TPMS systems and have many problems (in other words, they eat sensors) while pampered, sportier cars can have almost no problems at all. But in both cases, knowing a few practical tips can make TPMS service quicker and easier and keep the work problem-free.

No doubt the systems have evolved since they were introduced and can actually be simple to work on with the right tools and service information, but since there are still so many different systems on the roads (with unique methods of resetting and programming the systems and their related sensors) that it’s still important to refer to service information and be sure rather than guess and learn the hard way.

Fact is, the systems are safety-critical so they’re not going away any time soon.

TPMS systems are usually straightforward to deal with, and while you may not make a fortune servicing them you can definitely avoid costly problems and keep other work trouble-free and profitable.

With practical information and tips from hard-earned experience – plus service information and the right tools – working on TPMS systems successfully doesn’t need be a problem at all.

Sponsored Recommendations

ZEUS+: The Cutting-Edge Diagnostic Solution for Smart, Fast, and Efficient Auto Repairs

The new ZEUS+ simplifies your diagnostic process and guides you through the right repair, avoiding unnecessary steps along the way. It gives you the software coverage, processing...

Diagnostic Pre- and Post-scan Reports are Solid Gold for Profitability

The following article highlights the significance of pre-scans and post-scans, particularly with Snap-on scan tools, showcasing their efficiency in diagnosing issues and preventing...

Unlock Precision and Certainty: TRITON-D10 Webinar Training for Advanced Vehicle Diagnostics

The TRITON-D10 lets you dig deep into the systems of a vehicle and evaluate performance with comparative data, systematically eliminating the unnecessary to provide you with only...

APOLLO-D9: Trustworthy Diagnostics for Precision Repairs

The APOLLO-D9 provides the diagnostic information and resources you need to get the job done. No more hunting through forums or endlessly searching to find the right answers. ...

Voice Your Opinion!

To join the conversation, and become an exclusive member of Vehicle Service Pros, create an account today!